Lets talk Vapor pressure deficit (VPD) in cannabis?

[Douglas.Curtis]

Super hot/wet grows, eh? It's all about what your end goal is. IMO&E, Hot/wet grows tropical quality 'weight.' Significantly more plant cells/trichome than cool/dry, and not my cup of tea.

Compare my results to their results, using the same clone, and you'll prefer my results. If you're straight up cash cropping stay hot/wet for maximum weight. The masses are still ignorant.

 

[imakandi]

Super hot/wet grows, eh? It's all about what your end goal is. IMO&E, Hot/wet grows tropical quality 'weight.' Significantly more plant cells/trichome than cool/dry, and not my cup of tea.

Compare my results to their results, using the same clone, and you'll prefer my results. If you're straight up cash cropping stay hot/wet for maximum weight. The masses are still ignorant.

can share picture?
cool dry is no good for plant, i skepktik
but open mind
thank

 

[Ibechillin]

The highest cannabinoid landraces seem to come out of Malawi Africa and Thailand, I dont know if i agree with that logic DC. Seems more like 15 degrees north or south of the equator in tropic environments produces the highest quality cannabis.

^This is my thought process, its funny people have a hard time imagining obtaining quality and heavy yield. Maximize plant health and both increase, the OG heavy croppers didnt get where they were by pushing reggie...

 

[LEDAstray]

Might be useful for those wondering about lower leaf temps with LED. You can recalculate the chart with your specific leaf to air temp difference. I use an IR thermometer to give me a rough idea of leaf temps.......when I can be bothered.

https://opennlabs.com/vpd/VPD_calculator.php

 

[Douglas.Curtis]

can share picture?
cool dry is no good for plant, i skepktik
but open mind
thank

Here's a pic of 6 plants under a 1K HPS at 19 days, 68F incoming air, 20'ish RH. You MUST veg longer for the same yield as a hot/wet grow. There simply is no explosion of growth/stretch at flip. I want zero flower production in hot/wet, because it grows the wrong physical structure and cell structure.

^This is my thought process, its funny people have a hard time imagining obtaining quality and heavy yield. Maximize plant health and both increase, the OG heavy croppers didnt get where they were by pushing reggie...

I seem to have a completely different view of 'quality.' As far as I'm aware, there is no way to push maximum yield AND quality, because it's one or the other.

Sure, there's maximum yield for the maximum quality. However, this is a completely different conversation than one the "OG Heavy croppers" are chasing. They're chasing maximum yield first, best quality for that yield second. Keep in mind, the general public they're selling to is almost completely ignorant about quality.

The trichome density, minimalistic 'stem' content, frangibility and overall terpene retention of this flower, is not possible with a hot/wet grow.


(edit: The last several thousand years of 'premium' hash production, has all come from the cool/dry mountain areas of the planet. Not tropical. These conditions produce the highest trichome density, with the maximum terpene preservation throughout the flowering period. Sesquiterpenes are formed from monoterpenes, which a lot vape off at above 70F. )

 

[Veggia farmer]

I definitely chase maximum weight of the maximum quality that I can achieve, LOL!

I cant bitch about the resin of the last runs IMHO.. Its always a hash hit on the table after rolling one 70%RH..

I have heard earlier that dry in the end will give more resin... Hot will vape something I also read, you say 70F, DC? hmm..


As far as mold, not that big of a problem so long other things work.. air, temp etc.. living organic soil with fokus on silica and other minerals FTW.. Have had critical mass going 12-14 weeks without mold in this condition, yup, that was big buds..

Ibechillin, came here right after reading that coco tree thread. Maybe I try to bump it even more up one round to see..

 

[Veggia farmer]

What should be the science that could make dry air give more terps and resin? shouldn`t the oils be protected by the humidity?

 

[Ibechillin]

Here's a pic of 6 plants under a 1K HPS at 19 days, 68F incoming air, 20'ish RH. You MUST veg longer for the same yield as a hot/wet grow. There simply is no explosion of growth/stretch at flip.

Quote from article:

https://www.cannabisbusinesstimes.com/article/moisture-matters/

Plants acquire carbon dioxide from the atmosphere in which they are growing; this requires that the plants open their stomata and capture carbon dioxide. Opening the stomata also causes water to be drawn up through the plant from roots to shoots to the leaves and, ultimately, the atmosphere. This process causes the plant to acquire water from the soil medium, which is laden with nutrients. Therefore, the following can occur if humidity is not balanced correctly:

1. With very low humidity, the plant is drawing water from the soil at a very high rate, and if the humidity is too low, the plant is unable to draw water at a rate equal to loss through the stomatal openings. The result is that the plants close their stomata, which slows the photosynthetic process (due to carbon limitations) and leads to stress, slow growth and compromised yield. Under severely low humidity, the plant will wilt and die because even its protective mechanisms cannot offset the water stress imposed by the lack of atmospheric water.

2. When humidity is too high, the rate at which plants draw water from the soil is reduced because transpiration is slowed by the smaller-than-normal water gradient between the plant and the atmosphere. This can result in diminished nutrient uptake efficiency, which can lead to nutrient deficiencies. This phenomenon is particularly evident in the uptake of calcium.

Additionally, saturated media pH has a tendency to climb over time, which can also result in many nutrients (e.g., metals, phosphorus and calcium) becoming unavailable to the plant because of altered chemical interactions under elevated pH conditions.

What Are Optimal Humidity Levels?

While cannabis cultivation research is a growing field, scientific evidence characterizing optimal growing conditions has not been fully explored. Fortunately, a vast body of research exists in the areas of indoor and greenhouse cultivation of many food species. Some of these food crops are suitable surrogates for determining potential cannabis cultivation conditions because of similarities in natural, physiological and environmental requirements.

The general humidity range for indoor cultivation appears to exist between 60% and 75% for all growth stages. When humidity surpasses 80%, particularly during the lights-off phase, a higher risk of fungal, bacterial and viral infections exists. Conversely, if humidity drops much below 50%, crop photosynthetic efficiency may be affected and yield will suffer.

Based on peer-reviewed research in the field of indoor/greenhouse produce cultivation, the following relative humidity (RH) conditions would be suitable for indoor/greenhouse cannabis cultivation.

Cloning: 70%-75% RH
Vegetation: 65%-70% RH
Flower: 60%-65% RH
Night phase of flower: 55%-60% RH
Tips: Always be sure to avoid stagnant air during all light and dark phases and swap air to reduce humidity/carbon dioxide levels during light-dark-phase transitions. Finally, be sure your temperatures are suitable for optimal plant growth during light-phases (75°-80°F) and slightly cooler temperatures during dark-phases (~70°F).

Mark June-Wells is laboratory director for Connecticut Pharmaceutical Solutions (CPS), one of four licensed medical cannabis producers in the state. Dr. June-Wells holds a Ph.D. in botany/plant ecology from Rutgers University, and has engineered CPS’ cannabinoid extraction efficiency and tracking programs, developed one of the largest production databases in the United States, and created efficient and repeatable production methods informed by rigorous data collection and statistical model building.

 

[imakandi]

Here's a pic of 6 plants under a 1K HPS at 19 days, 68F incoming air, 20'ish RH. You MUST veg longer for the same yield as a hot/wet grow. There simply is no explosion of growth/stretch at flip. I want zero flower production in hot/wet, because it grows the wrong physical structure and cell structure.
[URL=https://www.icmag.com/ic/picture.php?albumid=70975&pictureid=1808355&thumb=1]View Image[/URL]


I seem to have a completely different view of 'quality.' As far as I'm aware, there is no way to push maximum yield AND quality, because it's one or the other.

Sure, there's maximum yield for the maximum quality. However, this is a completely different conversation than one the "OG Heavy croppers" are chasing. They're chasing maximum yield first, best quality for that yield second. Keep in mind, the general public they're selling to is almost completely ignorant about quality.

The trichome density, minimalistic 'stem' content, frangibility and overall terpene retention of this flower, is not possible with a hot/wet grow.
[URL=https://www.icmag.com/ic/picture.php?albumid=70975&pictureid=1689883&thumb=1]View Image[/URL]

(edit: The last several thousand years of 'premium' hash production, has all come from the cool/dry mountain areas of the planet. Not tropical. These conditions produce the highest trichome density, with the maximum terpene preservation throughout the flowering period. Sesquiterpenes are formed from monoterpenes, which a lot vape off at above 70F. )

is fine
you go against agriculture science

i think you create up a lot things
for your argument
but byology, plant science, plant physyology all say contrary

can always have diary to proof your say

but is fine
you is you
dont need argument, keep quality for you

 

[Fitzera]

You need to understand DC's train of thought to understand what hes doing in his grows.

Only so many trichomes are produced. The more plant cells (larger yield weight) between these trichomes, the less quality because there is less trichomelant material.

So by running lower temps/humidity, he is (as is stated in the write ups) limiting the overall plant growth and end yield result, but not the trichomes.

So he may have smaller flowers, but they should have a denser trichome coverage, equaling a heavier hitting bud when comparing by weight to flower grown to its yield potential.

Think of it this way, I'm sure weve all seen this in our own grows...those lower buds we like to take pictures of...they're small and undeveloped in size, but fuck me are they the most resinous looking buds on the plant. Right? Now look at them again when theyve filled out...what do you notice? They're not nearly as caked in trichomes as they were when they were small. Same trichome amount, but more plant material too now.

Make sense? This is how I've understood him, this is correct DC?

 

[Ibechillin]

.

 

[Douglas.Curtis]

Apologies, I've been laid up a few days and been off the comp till now.

Fitzera has it correct, and Ibechillin proves my point fairly well.

You need to understand DC's train of thought to understand what hes doing in his grows.

Only so many trichomes are produced. The more plant cells (larger yield weight) between these trichomes, the less quality because there is less trichomelant material.

So by running lower temps/humidity, he is (as is stated in the write ups) limiting the overall plant growth and end yield result, but not the trichomes.

So he may have smaller flowers, but they should have a denser trichome coverage, equaling a heavier hitting bud when comparing by weight to flower grown to its yield potential.

Think of it this way, I'm sure weve all seen this in our own grows...those lower buds we like to take pictures of...they're small and undeveloped in size, but fuck me are they the most resinous looking buds on the plant. Right? Now look at them again when theyve filled out...what do you notice? They're not nearly as caked in trichomes as they were when they were small. Same trichome amount, but more plant material too now.

Make sense? This is how I've understood him, this is correct DC?

Who here has thick puffy sugar leaves and physical flower structures? I see a lot of them all over the net, and all over this forum. They sure 'look' pretty. Here's a question though... WHY on earth would you find this a desirable trait for smoking??

Do you like smoking a dual layer of trichomes, double stuffed with a thick leafy material? Wouldn't you prefer a super slim leaf between your dense mats of trichomes? Just because it's fluffy doesn't make it tastier, it actually adds additional 'burnt plant yuck' to your smoke.

Yes I'm bucking the trend. I'm literally sick and tired of 'the trend.' Those who buck the trend and try being adventurous... end up not going back to hot/wet except for cash crops.

Ibechillin, you've brought an amazing amount of information to this forum, and I greatly appreciate your input. Unfortunately, your statement about cola size is a blatant declaration of how you're on the wrong track.

Do I know everything about this? Hell no! I've spent 15+ years with no budget, almost all homemade equipment, and (for many years) almost nothing but f'ing maxibloom + epsom. With cool/dry and proper res management, the quality beats anything I've seen in over 10 years now.

Try it. Come back and tell me different.

 

[Ibechillin]

We all have our own perspective/opinions of quality and unique experiences, I just share information.

 

[Douglas.Curtis]

We all have our own perspective/opinions of quality and unique experiences, I just share information.

I couldn't agree more, and everything and our opinions are relative to our own personal experiences. You've brought a wealth of information indeed.

My goal is to broaden people's awareness and bring them an experience they need. I challenge everyone to grow cool and dry at least once. From beginning of flower development, all the way through harvest. And be sure to stay cool through trimming and drying.

Doesn't work for you quality wise... I'll be very surprised.


(edit: FYI, I'm aware my diplomacy leaves a lot to be desired. I assure you and everyone, my intentions are honorable and for everyone's benefit.)

 

[Veggia farmer]

All I know is I know nothing.. Would be really cool to do experiment on it. Think I will, not soo long in the future. Same cut in hot/wet vs cool/dry.. Hot/wet vs hot/dry.. cool/wet vs cool/dry..

Jorge talks about Felix in his book. Crops higher in altitude has more thc in it. Maybe not just UV, but the temps???

Not sure if its a pattern to it, but it seems more leafy in cool rooms.. anyone?


I have a basement that Im first isolation next week after growing in it for some years.. Its always humid there(70%), but the temps is very variabel after the season (60+degress N), the buds is definitely more compact in winter ( and a hell of lot less yield LOL) but I have not seen quality improved, but two good eyes dont always see…(?) and yes, two critical mass cuts over and over again..


For instance strawberries, all import of it does not taste "strawberry" too us, yes, take that with some salt... Because our strawberry has more sun hours, but its also the lower temps that create this aroma, being just MORE aroma.. this is info from agriculture advisers here and the school I went too. Actually a lot of herbs have better medicinal quality being grown here instead of the warm south..

And again I went of topic, we talked about VPD..

 

[Douglas.Curtis]

Terribly sorry to derail the VPD discussion, I've started a thread for the cool/dry conversation. Doing my best to explain as much detail as I'm aware of on the subject.

Leafy is spectrum based, hot/dry is too much stress, cold/wet is lack of transpiration rate. Crops higher in altitude are smaller with the same trichome count, so more THC per square inch. Grapes must be stressed for premium flavor in wine making.

 

[Ibechillin]

Quality is proportionate to the ability to meet nutritional demand from what I understand, I feel it’s the missing link for most people that don’t have a solid comprehension of nutrient science. People constantly change environmental variables but feed the same premade fertilizer solutions that are typically far from ideal to begin with prioritizing shitty cell structure.

The science was proven quite a while ago, Albrecht, Tiedjens and Reams all came to the same conclusion, 85% Ca.

With that said, try going to the Italian and French Alps where the soil is 92-94% Ca and then come back after give us a full report after you have eaten one of the most amazing tomatoes, grapes, you name it... that you have ever eaten.

And as for Cannabis, we already did the THC numbers on a posted article that showed 82% Ca had the highest THC levels compared to the others which were in many cases were 20 to 30% of the THC that was achieved at the HIGHEST Ca%. Not sure which thread it was in. The article and the excel math sheet were all posted. Check it out.

What locks out nutrients is high pH.

High Ca does not mean high pH. Only if you use carbonates.

Gypsum won't raise the pH.

Read Albrecht's later work. 85% Ca in the base saturation.
Read Tiedjens, More Food from Soil Science. And then read it again and again. Again, 85% Ca.

Carey Reams, if you do the math on his formula, again, 85% Ca.

And just when you though 85% Ca was the answer... go to the French or Italian Alps and eat their grapes, produce etc. and you will say, Oh my God. What the hell is going on here? How did someone achieve this quality? Guess what? 92-94% Ca!

There is a good article that you can read Cannabinoid Profile and Elemental Uptake of Cannabis sativa L. as Influenced by Soil Characteristics by C. B. Coffman and W. A. Gentner.

https://www.votehemp.com/wp-content...s_Influenced_by_Soil_Characteristics-1975.pdf

If you do the math, you will quickly see that high Ca and P drove actives. The highest K and Mg had the lowest.

 

[f-e]

My head hurts. I can't compute 85% Ca. I have Defra guidance here, where a very quick look at mg/l of the bases, says maybe 50% at a push. So I looked at cannabis leaf tissue samples, and found that 85% Ca would mean 12% Mg, leaving just 3% and we haven't done K yet. Which might be 60. It seems so wrong.

If you want to help trich production, think silicone. It won't effect potency, but is very easy to assimilate.

I keep healthy plants, which quite beyond my control, give me a good yield. I have tried doing worse, really I have, but I didn't like it. The idea of holding them back with cool temps is appealing, but the cold just grows leafy green for me. Lacking flavour, not preserving it. The buds offered as evidence don't really stand out beside most white strains. Which under good light, can glisten like precious stones. But are no stronger and taste very mild. Looks are basically no gauge of flavour or strength, unless it's huge great buds that obviously came off a healthy plant.


So.. VPD. Pretty much no talk about vapour pressure and it's effect on transpiration as an almost hydraulic process. I don't really want to go there either. I think we have what we need.

So the sudden crash in RH at lights on. Is it good reason to bring the lights on in sets over half an hour. I'm doubtful, but the drop is considerable.

 

[Ibechillin]

Hard to say the proof is in the pudding until you have had the pudding, no?

I am not saying that there is not excellent quality weed out there, what I am saying is that after you have tried something grown correctly using real science, you will then understand there is a whole other universe out there that you didn't know existed.

This is the thread the slownickel quotes are from if interested in reading/learning more:

incorrect npk and supplement ratios are some of the reasons for shitty bud:

https://www.icmag.com/ic/showthread.php?t=348825&highlight=Alps

 

[Douglas.Curtis]

The idea of holding them back with cool temps is appealing, but the cold just grows leafy green for me. Lacking flavour, not preserving it.

What spectrum are you running? Under HPS and around 3K LED, there is no 'leafy' response to cooler and drier temps. You're also missing something in the environment or the flavors and aromas would be stronger instead of weaker. Check out the thread I started and perhaps you'll figure it out quicker.

The buds offered as evidence don't really stand out beside most white strains. Which under good light, can glisten like precious stones. But are no stronger and taste very mild. Looks are basically no gauge of flavour or strength, unless it's huge great buds that obviously came off a healthy plant

Yes, I've had plenty of very frosty cannabis which was a huge disappointment. Disappointment is not what you get when you grow the way I do.

What's needed is a 'typical' flower photo from the same cut. The original cut of "Pink" is not a frosty strain, it only looks like my photo when grown cool and dry. Here's a larger photo with more detail. I don't suppose anyone else has a photo of "Pink" from Avi a few years ago?